360 build update

yeah idk, tomorrow I will put in a new front o2 and a new crank sensor. An ill also have Sean send a tune with more fuel across the bord not allot just a small amount more to see if it gets better.

what I dont understand is someone told me running lean will cause backfiring out the intake....how does that work? Lean or not why would the valve not be closed and backfire out the exhaust?

just thinking in type here.. i suppose the combination of the dizzy being 16* advanced and the throttle body leak could cause a lean condition.
cause of the leak, smity, was the IDLE high. should have been!

Hey Smity! Have you had a fuel pressure gauge on the fuel rail to monitor pressure? I'm still surprized it don't throw a code. Try unpluging your IAC and see it that helps.

Originally Posted by spun360

just thinking in type here.. i suppose the combination of the dizzy being 16* advanced and the throttle body leak could cause a lean condition.
cause of the leak, smity, was the IDLE high. should have been!

Originally Posted by Lee Peterson

Hey Smity! Have you had a fuel pressure gauge on the fuel rail to monitor pressure? I'm still surprized it don't throw a code. Try unpluging your IAC and see it that helps.

Idle should be at 750 want to say it was close to 900 ill double check tomorrow, and ill unplug the IAC

Oh did I mention that there was no test port for my fuel rail so we had to cut the hose that connects the two rails and put a T in it and clamp it down, wonder if its restricting fuel ill buy a new house tomorrow and take the sensor out see if it helps

think dorman has those lines. you got to heat them up, put it on quickly, and let it cool down before you charge the system. a heat gun on low is helpful, dont burn it.

Originally Posted by spun360

think dorman has those lines. you got to heat them up, put it on quickly, and let it cool down before you charge the system. a heat gun on low is helpful, dont burn it.

Braded hose with hose clamps work just good lol not getting fancy. New TB Gasket going on in a few, Cank Sensor, and front o2 if it aint fixed after this guys....theres nothing more I can do. An Sean sent me a tune with a little more fuel across the bord both WOT Part Throttle and while Idling will see if that helps after all these other test.

The only other thing I can think of is cam sensor under the dizzy cap. But when mine went bad on my 96 it threw a code. Maybe some dirt got in an injector. Do you have a scanner that can monitor long term and short term fuel trims?

Truck runs like a raped ape now that its got fuel, crank sensor didn't change anything, changed o2 put the fuel tune in truck hit 100mph, getting a few pops here and there but under 2000 I can stomp it without it backfiring, still backfires a little, hes going to fine tune the rockers by turning then while there moving.....so happy hahaha, deffly need rotor conversion for the back hard time stopping

Its weird it needs fuel added, wondering if an injectors are dirty. Stock fuel injectors are 23.5lbs thats all I have and Sean cut fuel at idle.

You should set your fuel sync to +4 with a scanner. My pic was just ruff position.

Good that it's better now though, atleast you can drive it.

Originally Posted by Lee Peterson

Its weird it needs fuel added, wondering if an injectors are dirty. Stock fuel injectors are 23.5lbs thats all I have and Sean cut fuel at idle.

You should set your fuel sync to +4 with a scanner. My pic was just ruff position.

Good that it's better now though, atleast you can drive it.

Do you have a 2.02 intake valve...It makes sense to me, I have bigger intake valves, and intake that sucks allot of air....he said he was cutting like 25% fuel...it idles great wideband reads between 14.7-15.8 it bounces....just driving down the road 14.7 all day.....before it was like 17.5. When you stomp on it it will hit 13ish on the wide ban and the lowest i've seen it go at WOT was 12.5 so probably could use a little less but for now im not messing with it. Want to drive it let it learn itself for a while.

Bad news though is got a leak in the rear main have to fix that. Worse news was my buddy is just a idiot. Smart kid but I will never let him work on my (engine) again. Rear ends lift kits welding ill go to him but just saw allot of hack job stuff done. To top it off the rotatella T oil he had me use and said they still have zinc in it....DOESN'T! I broke that motor in without zink in the oil, im surprised that the 6 rings that seated even seated....so I picked up the ZDDP additive today and will add it after I fix the rear main leak.

Originally Posted by Lee Peterson

Its weird it needs fuel added, wondering if an injectors are dirty. Stock fuel injectors are 23.5lbs thats all I have and Sean cut fuel at idle.

You should set your fuel sync to +4 with a scanner. My pic was just ruff position.

Good that it's better now though, atleast you can drive it.

Why plus 4 why not leave it at 0 were its at?

Just because you cams +4 advanced from comp. I know mine poped every onces and a while with it set to +1. It would pop right off idle. For WOT 12.5 Is about where you want to be.

Do you have a good camera yet? Get some videos up.

Originally Posted by Lee Peterson

Just because you cams +4 advanced from comp. I know mine poped every onces and a while with it set to +1. It would pop right off idle. For WOT 12.5 Is about where you want to be.

Do you have a good camera yet? Get some videos up.

I do videos will come soon enough, trucks still not home, still having some fine adjustment on the rockers hes giving them some more pre load as its running just enough to where they stomp chattering. Then there its the rear main issue. Then some full blown abuse videos lol.

So what actually fixed the low rpm back firing? It seems like you fixed a lot of stuff at once.

Originally Posted by madmikeismad

So what actually fixed the low rpm back firing? It seems like you fixed a lot of stuff at once.

The crank sensor did nothing. We swapped it out started the truck still backfired, then we downloaded seans fuel adding tune and changed the front o2 which did look beat up......took it for a test drive after letting it idle for a bit to learn itself did some daily driving and some fast acceleration it kept getting better and better.

Sometimes you just got to listen to the engine, wideband said lean, spark plugs were starting to get white, everything pointed to not enough fuel and in the end thats what it was.

Like I said from the start it was running lean!! Lol . Your truck should be ready today.

Originally Posted by Bigjim6886

Like I said from the start it was running lean!! Lol . Your truck should be ready today.

There was no doubt it was running lean question was why. Let me know if you can spin your tires with 4.56 gears. I got 3.92 and can barley spin them. I might go back to my 206 cam, it would light the tires for 5 feet in my 318.


From Manual.

During Closed Loop modes, the PCM will monitor
the oxygen (O2S) sensors input. This input indicates
to the PCM whether or not the calculated injector
pulse width results in the ideal air-fuel ratio. This
ratio is 14.7 parts air-to-1 part fuel. By monitoring
the exhaust oxygen content through the O2S sensor,
the PCM can fine tune the injector pulse width. This
is done to achieve optimum fuel economy combined
with low emission engine performance.

When engine has reached operating temperature,
the PCM will begin monitoring O2 sensor
input.